The anisotropic resistivity components of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_4$${\mathrm{O}}_8$ have been measured from 0 to 900 K. ${\mathrm{YBa}}_2$${\mathrm{Cu}}_4$${\mathrm{O}}_8$ is an underdoped, genuinely untwinned, and stoichiometric high temperature superconductor. The ${\mathrm{CuO}}_2$ plane resistivity ${\mathrm{\rho }}_{\mathit{a}}$ exhibits a strong correlation with the spin dynamics, i.e., with Knight shift and spin-lattice relaxation time ${\mathit{T}}_1$. The resistivity along the b axis (plane plus chain) is consistent with Bloch-Grüneisen theory. The cotangent of the Hall angle is quadratic in temperature above the spin gap, and linear below.

• Received 2 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.2012